Increasing demand for high quality images for an image acquisition device such as a camera requires high-quality image acquisition technology. For example, adoption and application of an optical image stabilizer (OIS) for preventing image damage due to hand tremor have been attempted. Such an OIS is applied to cellular phones and small mobile devices in addition to digital cameras.
Furthermore, an auto focus (AF) system is widely used as a high-quality image acquisition technology. An AF system employing phase difference detection or contrast detection is one form of such an AF system.
Particularly, an AF system employing phase difference detection arranges a pair of focus detection pixels in an image sensor for focus control.
The AF system employing phase difference detection calculates a focus deviation by forming a pair of images using an image sensor in which focus detection pixels are arranged and measuring a distance between the formed images. Then, the AF system controls focus by predicting a movement amount of an image pick-up lens on the basis of the focus deviation and adjusting the position of the image pick-up lens on the basis of the movement amount. Such a phase difference detection AF system has been widely applied recently as a system having higher accuracy than a contrast detection system.
However, when the phase difference detection AF system and the OIS are simultaneously applied to an image acquisition device, an optical signal input to an image sensor becomes unstable when the OIS is driven for image stabilization, causing a problem that a phase difference value detected by the AF system differs from that detected when the OIS is not driven.